This invention relates to the control of a heating, ventilation and air-conditioning (HVAC) system in a motor vehicle that is capable of being remotely started, and more particularly to a method of automatically pre-heating or pre-cooling the vehicle cabin following a remote start.
An increasing number of motor vehicles are being equipped, most commonly as an aftermarket accessory, to enable remote starting of the vehicle engine. The primary purpose of remote starting is to pre-cool or pre-heat the vehicle cabin, particularly when the vehicle is parked outside during extreme hot or cold weather conditions, so that the cabin will be more comfortable when entered by the occupants. In a cold climate, additional measures may be taken to clear the windows of frost or snow by activating the defroster, the rear window defogger and the wipers, for example. With automatic HVAC systems, most of the required control functions occur automatically so long as the system is left in the automatic (AUTO) mode, whereas with manually controlled HVAC systems, the driver must ordinarily select appropriate blower, temperature, mode and air conditioning settings prior to exiting the vehicle. While various control strategies have been developed for essentially automating the pre-cooling or pre-heating functions in manually controlled HVAC systems, such controls are either pre-programmed, or require temperature sensors that are not typically available in a vehicle equipped with a manually controlled HVAC system. For example, the systems disclosed in the U.S. Pat. Nos. 4,436,064 and 5,791,407 require outside air and cabin air temperature sensors. Accordingly, what is needed is an improved remote-start HVAC control method that utilizes commonly available sensor information to provide appropriate pre-heating or pre-cooling of the vehicle cabin.
The present invention is directed to an improved method of activating a manually controlled HVAC system for automatically pre-heating or pre-cooling the vehicle cabin following a remote start, wherein commonly available engine and HVAC sensor information is utilized to activate and maintain appropriate HVAC settings. When the engine has been remotely started, an HVAC controller estimates initial outside air and cabin air temperatures, and determines if pre-heating or pre-cooling is appropriate based on the estimated initial temperatures, the engine coolant temperature and a measure of the engine soak time. When pre-heating or pre-cooling is deemed to be appropriate, the HVAC parameters normally set by a driver interface panel are selectively overridden based on the estimated initial outside air and cabin air temperatures. In a particularly advantageous embodiment, the initial outside air temperature is estimated based on an inlet air temperature sensor of the engine or on a refrigerant pressure sensor of the HVAC system prior to activation of the refrigerant compressor.